Method and system for diesel cylinder deactivation

ABSTRACT

A system and method for cylinder deactivation in a multi-cylinder diesel engine comprises pumping air in to an intake manifold of the diesel engine using a turbocharger. Air is pumped in to the intake manifold using an intake air assisting device. And, fuel injection is selectively deactivated to at least one of the cylinders in the diesel engine. An intake valve and an exhaust valve is selectively deactivated for the at least one of the cylinders of the diesel engine.

This application claims priority to and is a continuation of U.S. patentapplication Ser. No. 15/323,415 filed Dec. 31, 2016 and entitled “Methodand System for Diesel Cylinder Deactivation,” which is a National StageEntry of PCT/US2016/013863 filed Jan. 19, 2016, which claims the benefitof U.S. provisional application 62/104,989 filed Jan. 19, 2015, all ofwhich are incorporated herein by reference in their entirety.

FIELD

This application relates to diesel engine fuel management techniques.and provides a method and system for extending cylinder deactivation tomid-range engine loads.

BACKGROUND

It is possible to control combustion processes in diesel engines tolimit the number of cylinders providing torque output. One technique iscylinder cut-out. The technique eliminates fuel to a cylinder whilecontinuing to cycle the intake and exhaust valves. The piston alsocycles. The technique results in fuel economy losses.

At very low loads and idle conditions, an engine runs with poor fuelefficiency. All cylinders are firing, but little to no torque output isneeded. Even in a loaded idle condition, the engine could provide moretorque than necessary. Fuel is wasted, and the fuel economy is poor.

The low, and inefficient, fuel use is not effective to heat theaftertreatment system, and so pollution is high.

It would be beneficial to improve fuel economy and fuel efficiency in adiesel engine. It is beneficial to reduce pollution.

SUMMARY

The disclosure overcomes the above disadvantages and improves the art byway of a system and method for cylinder deactivation in a multi-cylinderdiesel engine, comprising pumping air in to an intake manifold of thediesel engine using a turbocharger. Air is pumped in to the intakemanifold using an intake air assisting device. And, fuel injection isselectively deactivated to at least one of the cylinders in the dieselengine. An intake valve and an exhaust valve is selectively deactivatedfor the at least one of the cylinders of the diesel engine.

A multiple cylinder diesel engine system comprises a multiple cylinderdiesel engine comprising a respective intake valve and a respectiveexhaust valve for each of the multiple cylinders. An intake manifold isconnected to supply air to the multiple cylinders of the diesel engine.An exhaust manifold is connected to receive exhaust from the multiplecylinders of the diesel engine. An intake air assisting device isconnected to pump air in to the intake manifold. A valve control systemis connected to selectively deactivate a respective intake valve and arespective exhaust valve for a cylinder of the multiple cylinder dieselengine. A fuel injection control system is connected to selectivelydeactivate fuel injection to the cylinder. The multiple cylinder dieselengine enters a cylinder deactivation mode whereby the valve controlsystem deactivates the respective intake valve and the respectiveexhaust valve for the cylinder. The valve control system deactivatesfuel injection to the cylinder while other cylinders of the multiplecylinder diesel engine continue to fire.

A pollution management system for a diesel engine, comprises a dieselengine comprising a plurality of combustion cylinders. Each of theplurality of combustion cylinders comprises a respective pistonconnected to a crankshaft, a fuel injector connected to an injectioncontroller, an intake valve connected to an intake valve controller, andan exhaust valve connected to an exhaust valve controller. An exhaustsystem is connected to the exhaust valves. The exhaust system comprisesa catalyst for filtering pollution from an exhaust stream and a sensorfor measuring a pollution level in the exhaust stream. A control unitcomprises a processor, a memory device, and processor-executable controlalgorithms stored in the memory. The control algorithms are configuredto receive pollution level sensor data from the sensor, determine apollution level in the exhaust stream, and determine whether thepollution level exceeds a pollution threshold. When the pollution levelin the exhaust stream exceeds a pollution threshold, the control systemselects at least one of the plurality of combustion cylinders fordeactivation, commands the injection controller to deactivate therespective fuel injector for the at least one of the selected combustioncylinders, commands the intake valve controller to deactivate therespective intake valve for the at least one of the selected combustioncylinders, and commands the exhaust valve controller to deactivate therespective exhaust valve controller for the at least one of the selectedcombustion cylinders.

A method for operating a multiple cylinder diesel engine system in acylinder deactivation mode comprises determining that the diesel enginesystem is operating within at least one threshold range. Cylinderdeactivation mode is entered in at least one cylinder of amultiple-cylinder diesel engine when the diesel engine system isoperating within the at least one threshold range. An air fuel ratio isadjusted to at least one firing cylinder of the multiple-cylinder dieselengine based on the entering of cylinder deactivation mode in the atleast one cylinder. Entering cylinder deactivation mode comprisesdeactivating fuel injection to the at least one cylinder anddeactivating intake valve actuation and exhaust valve actuation to theat least one cylinder.

Additional objects and advantages will be set forth in part in thedescription which follows, and in part will be obvious from thedescription, or may be learned by practice of the disclosure. Theobjects and advantages will also be realized and attained by means ofthe elements and combinations particularly pointed out in the appendedclaims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the claimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A & 1B are schematics for an engine system.

FIG. 2 is a schematic for another engine system.

FIGS. 3A-3C are alternate views of an example engine.

FIGS. 4A & 4B are example methods for implementing cylinderdeactivation.

FIG. 5 is an example of a 6-cylinder engine in normal mode.

FIG. 6 is an example of the 6-cylinder engine of FIG. 5 in cylinderdeactivation mode.

FIG. 7 is an example of exhaust temperature profile for an exampleengine.

FIG. 8 is an example of load thresholds for implementing cylinderdeactivation modes, normal mode, or augmented modes.

FIG. 9 is an example of load thresholds versus the number of cylindersin cylinder deactivation mode.

FIG. 10 illustrates an example brake thermal efficiency versus load foran engine.

FIG. 11 illustrates a polynomial curve linking turbine out temperatureto air fuel ratio.

FIG. 12 is an example of NOx pollution conversion efficiency versustemperature for a catalyst.

FIG. 13 is a chart contrasting NOx conversion efficiency to catalysttemperature, engine-out NOx, and tailpipe emission requirements.

FIG. 14 is a schematic of a computer control system for an enginesystem.

FIG. 15 is an example of possible intake or exhaust valve lift profiles.

FIGS. 16A-16D contrast 3-cylinder CDA mode against 6-cylinder mode forvarious outputs of an example engine.

DETAILED DESCRIPTION

Reference will now be made in detail to the examples which areillustrated in the accompanying drawings. Wherever possible, the samereference numbers will be used throughout the drawings to refer to thesame or like parts. Directional references such as “left” and “right”are for ease of reference to the figures.

Cylinder deactivation (CDA), where the intake valve, exhaust valve, andfuel injection are shut off for a selected cylinder cycle, is notobvious for diesel engines for several reasons. Many benefits inure andcan be used to improve fuel economy and pollution control. Contrary toprior research, CDA can be used to benefit fuel economy and pollutioncontrol in heavy machinery and light auto. For example, low loadcylinders can be deactivated to yield a fuel economy increase. Theefficiency of the engine increases because of a reduction in frictionvia elimination of valve motion. Further, turning off in-efficientcylinders to increase the efficiency of other cylinders improves fueleconomy over-all.

Cylinder deactivation differs from “cylinder cut-out,” which merelyturns off fuel injection to a chosen cylinders, but leaves affiliatedvalves in motion. Cylinder cut-out results in measurable and detrimentalsystem losses. Cylinder deactivation, however, achieves measurablesystem gains. As cylinders are deactivated, other firing cylinders mustincrease their torque output (load) to maintain the user experience.Increasing the load on the firing cylinders increases their fuelefficiency & brake thermal efficiency. Deactivating the intake andexhaust valves on the deactivated cylinders reduces energy losses tomove those valves, which increases fuel economy.

CDA can be used during certain duty cycles. For example, when on thehighway, heavy duty trucks can turn off CDA for high speed or cruisingduty cycles. But, for example, a garbage truck can use CDA throughoutthe pickup duty cycle. The same can be applied to a bus for a transportversus a pick-up duty cycle.

Normal operation of a 3, 4, 5, 6, 8, or 10 cylinder diesel engineinvolves inducing air into the intake manifold, closing valves on thecylinders, injecting fuel, igniting the fuel for combustion, andemptying the cylinder for the next cycle.

When the operating conditions do not require full torque output, it ispossible to limit which cylinders receive fuel, and it is furtherpossible to tailor the amount of fuel injected in to the individualcylinders. For example, it is possible to run the engine at 50% loadcapacity by deactivating fuel injection to half of the cylinders whileusing the remaining cylinders at full torque capacity. An even number ofcylinders can be deactivated to balance torsion across the engine, butit is also possible to deactivate a single cylinder, or another oddnumber of cylinders, to receive fuel efficiency benefits. The fuelefficiency of the fully used cylinders is extremely high, while there isno fuel use in the deactivated cylinders. The overall fuel efficiencyfor the motive device is improved, and fuel consumption is reduced. Thestrategy permits tailoring the torque output to the driving conditions.Using a six cylinder engine as an example, it is possible to deactivate2 or 4 cylinders while fully or partially using the torque outputcapacity of the remaining cylinders.

Turning to FIG. 1A, a schematic for an engine system is shown. An engine100 comprises 6 cylinders 1-6. Other numbers of cylinders can be used,but for discussion, 6 cylinders are illustrated. The cylinders 1-6receive intake fluid, which is combustion gas, such as air, or air mixedwith exhaust (exhaust gas recirculation “EGR”), from the intake manifold103. An intake manifold sensor 173 can monitor the pressure, flow rate,oxygen content, exhaust content or other qualities of the intake fluid.The intake manifold 103 connects to intake ports 133 in the engine blockto provide intake fluid to the cylinders 1-6. In a diesel engine, theintake manifold has a vacuum except when the intake manifold is boosted.CDA is beneficial, because the cylinder can be closed. Instead ofpulling the piston down against a vacuum situation, the deactivatedcylinder has a volume of fluid that is not at a vacuum. Fuel efficiencyis gained by not drawing the piston down against a vacuum.

Fuel is injected to individual cylinders via a fuel injection controller300. The fuel injection controller 300 can adjust the amount and timingof fuel injected in to each cylinder and can shut off and resume fuelinjection to each cylinder. The fuel injection for each cylinder 1-6 canbe the same or unique for each cylinder 106, such that one cylinder canhave more fuel than another, and one cylinder can have no fuelinjection, while others have fuel.

A variable valve actuator (VVA) 200 also couples to the cylinders 1-6 toactuate intake valves 130 and exhaust valves 150. The VVA 200 can changethe actuation of the intake valves 130 and exhaust valves 150 so as toopen or close the valves normally, early, or late, or combinationsthereof, or cease operation of the valves. Early Intake Valve Opening(EIVO), Early Intake Valve Closing (EIVC), Late Intake Valve Opening(LIVO), Late Intake Valve Closing (LIVC), Early Exhaust Valve Opening(EEVO), Early Exhaust Valve Closing (EEVC), Late Exhaust Valve Opening(LEVO), Late Exhaust Valve Closing (LEVC), a combination of EEVC andLIVO or Negative Valve Overlap (NVO) can be implemented by the VVA 200.VVA 200 can cooperate with a hydraulic, electric, or electric solenoidsystem to control the intake and exhaust valves 130, 150. The engine 100can be cam or camless, or a hybrid “cam-camless VVA.” So, the intake andexhaust valves 130, 150 can either couple to a cam system for actuation,as the camshafts 801, 802 example of FIG. 3A, a hydraulic rail, alatched rocker arm, other rocker arm, an electro hydraulic actuator,etc. Or a cam less direct acting mechanism can selectively operate theindividual valves. While FIGS. 3B &3C show one intake valve 130 and oneexhaust valve 150, it is possible to have two intake valves 130 and twoexhaust valves 150 per each cylinder, as in FIG. 3A. The engine block102 is removed for the example of FIG. 3A for clarity, and the cylindersare shown in broken lines.

A diesel engine works by compressing intake fluid in a cylinder 1-6using a piston 160. Fuel is injected via fuel injector 310. The highheat and compression ignites the fuel, and combustion forces the pistonfrom top dead center (TDC) to bottom dead center (BDC) and torque isthereby directed to the crankshaft 101. Diesel operation can be referredto as “4 stroke,” though other operation modes such as 2-stroke and8-stroke are possible. In 4-stroke, the piston moves from TDC to BDC tofill the cylinder with intake fluid (stroke 1). The start of the cycleis shown in FIG. 3B, and FIG. 3C shows the end of stroke 1, when thecylinder is full of intake fluid. The piston rises back to TDC (stroke2). Fuel is injected and ignites to push the piston 160 to BDC (stroke3). The piston rises again to TDC to expel the exhaust out the exhaustvalve (stroke 4). The intake valve 130 is open during stroke 1 andclosed during strokes 2-4, though the VVA 200 can adjust the timing ofopening and closing. The exhaust valve 150 is open during stroke 4 andclosed during strokes 2-4, though the VVA 200 can adjust the timing ofopening and closing.

Exhaust gases leave cylinders through exhaust ports 155 in engine block102. Exhaust ports 155 communicate with an exhaust manifold 105. Anexhaust manifold sensor 175 can monitor the pressure, flow rate, oxygencontent, nitrous or nitric oxide (NOx) content, sulphur content, otherpollution content or other qualities of the exhaust gas. Exhaust gas canpower a turbine 510 of a variable geometry turbocharger (VGT) 501 orother turbocharger. The turbocharger 501 can be controlled via aturbocharger controller 500 to adjust a coupling 514 between the turbine510 and the compressor 512. The VGT can be adjust so as to controlintake or exhaust flow rate or back pressure in the exhaust.

Exhaust gas is filtered in an aftertreatment system. The aftertreatmentsystem can include a variety of pollution management mechanisms such asa hydrocarbon, fuel or urea doser. Several filters can be alone or incombination, such as DOC, DPF, SCR, NH3, Cu-Ze SCR, among others. One ormore catalyst 800 filters pollution, and can comprise a dieselparticulate filter (DPF), Diesel catalysts typically comprise a varietyof rare earth metals to filter pollution, including NOx. At least oneexhaust sensor 807 is placed in the aftertreatment system to measureexhaust conditions such as tailpipe emissions, NOx content, exhausttemperature, flow rate, etc. The exhaust sensor 807 can comprise morethan one type of sensor, such as chemical, thermal, optical, resistive,velocity, pressure, etc. The exhaust sensor 807 can comprise an array ofsensors, with sensor distribution options including before, after, orwithin the catalyst 800. A sensor linked with the turbocharger 501 canalso be included to detect turbine and compressor activity.

Exhaust can exit the system after being filtered by the at least onecatalyst 800. Or, exhaust can be redirected to the intake manifold 103via a variety of pathways, some of which are illustrated in FIGS. 1A-2.In FIG. 1A, exhaust is cooled in an EGR cooler 455. An EGR controller400 actuates an EGR valve 410 to selectively control the amount of EGRsupplied to the intake manifold 103. The exhaust recirculated to themanifold 103 impacts the air fuel ration (AFR) in the cylinder. Exhaustdilutes the oxygen content in the manifold 103. Unburned fuel from thefuel doser, or unburned fuel remaining after combustion increases thefuel amount in the AFR. Soot and other particulates and pollution gasesalso reduce the air portion of the air fuel ratio. While fresh airbrought in through the intake system 700 can raise the AFR, EGR canlower AFR, and fuel injection to the cylinders can lower the AFRfurther. Thus, the EGR controller, fuel injection controller 400 andintake assist controller 600 can tailor the air fuel ratio to the engineoperating conditions by respectively operating EGR valve 410, fuelinjector 310, and intake assist device 610. So, adjusting the air fuelratio to a firing cylinder can comprise one of boosting fresh air to theat least one firing cylinder by controlling a supercharger, ordecreasing air fuel ratio to a firing cylinder by boosting exhaust gasrecirculation to the firing cylinder. This can be done with or withoutaugmenting a turbocharger 501.

Variant engine system 12 in FIG. 1B removes one exhaust gasrecirculation path in favor of alternate pathways. EGR controller 400can couple instead to EGR valve 412 to direct exhaust gas along secondEGR path 613, along EGR path 612 to intake air assisting device 601.Alternatively, exhaust gas can be recirculated after being filtered bycatalyst 800. So EGR valve 414 can be controlled by EGR controller 400to direct some portion of EGR along first EGR path 610, along EGR path612, to intake assisting device 601. Controlling EGR valve 412 or EGRvalve 414 tailors the amount of exhaust included in the air fuel ratiowithin cylinders 1-6.

FIG. 16B compares the air fuel ratio (AFR) to the load (torque infoot-pounds) for an example 6-cylinder engine in normal mode (triangles)versus CDA mode (circles). Deactivating half of the cylinders cuts theAFR. At some point, the AFR becomes too low, and a soot problem arises.

Using a very small intake assist device 601 extends the operating rangeof cylinder deactivation (CDA) by boosting the available oxygen. A smallair pump, supercharger, or fan is connected to an oxygenating source,such as intake system 700, The intake system can supply fresh air toincrease the air fuel ratio in the intake manifold of the diesel engine.Instead of limiting CDA to low load or idle conditions, the intakeassist device 601 can increase air flow to the intake manifold and canincrease the air to the cylinders. This can provide a more lean burnengine by raising the air portion of the AFR. While it is possible tolower the AFR during cylinder deactivation (CDA) mode, the intake assistdevice makes it possible to increase the AFR by adding flow against alow pressure intake manifold. This is contrary to the prior art, whichseeks to eliminate energy drains during CDA mode. EGR does not need tobe suspended to limit CO2 contributions, but it can be regulated.

By controlling the air fuel ratio to the cylinders 1-6, it is possibleto eliminate the turbocharger 501, thus simplifying the controlalgorithm outputs and reducing system outlay. In FIG. 2, theturbocharger 501 is eliminated. Fresh air can be naturally aspiratedthrough the intake system 700 to the intake manifold 103, and the intakeassist device 601 can be selectively controlled to boost the intake flowto the intake manifold 103. Should the intake assist device heat theintake flow, such as when using a supercharger, a charge air cooler 650can optionally be included to regulate intake flow temperature. Asdiscussed in more detail below, the use of cylinder deactivation in lowload and idle modes, and boosting intake via the intake assist device601 in medium load modes eliminates the diesel engine system reliance ona turbocharger for air flow to the intake manifold 103.

FIG. 5 shows a normal operation mode for an engine system 10, 12 or 14or like engine system. Intake fluid 720 is provided to each cylinder1-6. Each cylinder receives fuel 320 and conducts a combustion cycle.Exhaust 420 exits each cylinder 1-6. A normal mode can be used hereinduring certain load and speed conditions of the engine, such as whenfull torque output is desired. Or, as when a cruising mode provides abetter temperature or NOx output for the engine system than CDA mode.

FIG. 6 shows cylinder deactivation mode (CDA). Half of the cylinders aredeactivated. Cylinders 1-3 receive fuel commensurate with the torqueoutput requirement. When the engine is required to maintain a certaintorque level, and CDA mode is implemented, it is possible to deactivatecylinders 4-6 while doubling fuel to cylinders 1-3. Because of fueleconomy benefits that inure from decreased friction on the totality ofcylinders, it is possible to provide less than double the fuel to thefiring cylinders 1-3 to obtain the same torque level as firing all sixcylinders in normal mode. For example, when shutting off half of thecylinders, the firing cylinders could receive 1.95 times more fuel tomaintain steady torque output during deactivation. So, CDA mode yields afuel economy benefit by decreasing fuel use for a desired torque output.

Intake and exhaust valves 130, 150 move as controlled by VVA 200 forfiring cylinders 1-3. However, intake and exhaust valves 150 are notactuated for cylinders 4-6.

Increasing the fuel to cylinders 1-3 makes the mixture in the cylinders1-3 more “rich.” The air fuel ratio for the cylinder is lower, becausethere is less air and more fuel. The resulting exhaust is hotter, asshown in FIG. 11. As the air fuel ratio nears a lower limit, the turbineout temperature (TOT) increases. Diesel engine system 14 does not use aturbocharger 501, and so “turbine out temperature” is used as a phraseof convenience to indicate the exhaust temperature at a location aturbine 501 would be. The TOT follows a polynomial curve as AFRincreases.

Unlike gasoline engines, which must be a stoichiometric 17:1 AFR(seventeen parts air to one part gasoline), diesel systems can vary theAFR and still work. The AFR in a firing cylinder can range from17:1-100:1 (seventeen parts air to one part diesel fuel up to 100 partsair to one part diesel fuel). Soot is an issue at low AFR, and so it isbeneficial to keep the AFR 22:1-24:1 when high temperature operation isdesired. To avoid soot, adjusting the air fuel ratio to a firingcylinder comprises adjusting one or both of the intake gases and thefuel injection to maintain an air fuel ratio of seventeen parts air toone part fuel or greater. CDA mode can operate with an AFR between17:1-70:1, or 20:1-50:1. Another AFR range is 24:1-45:1. One AFR rangefor providing an aftertreatment catalyst bed temperature around 300degrees Centigrade is 30:1-45:1 AFR.

Because of the polynomial relationship between AFR and TOT, it ispossible to develop a control algorithm for sensing a low temperaturecondition and adjusting the air fuel ratio to bring the exhausttemperature to a desired range. Using the above exhaust gasrecirculation (EGR) controller 400, fuel injection controller 300 andintake assist controller 600 is one aspect of regulating the exhausttemperature. Entering cylinder deactivation (CDA) mode on selectcylinders is another aspect of adjusting AFR and TOT.

FIG. 16A contrasts normal operation mode for a 6-cylinder engine(triangles) against a 3 cylinder CDA mode (circles). The load (torque infoot-pounds) is compared to the TOT in degrees Centigrade. 6-cylindermode has lower TOT than 3-cylinder CDA mode. Implementing the method ofFIG. 4A thus improves TOT. Additional TOT advantages inure when themethods of FIG. 4B are implemented.

Entering CDA mode reduces air flow through the engine 100. This is shownin FIG. 16C, where for a given load (torque in foot-pounds), the freshair flow (in kilograms per minute) is shown for a 6-cylinder mode(triangles) for an engine and for a 3-cylinder CDA mode (circles). Usingall 6 cylinders draws more air through the engine. Less air is drawnthrough the engine in CDA mode and pushed in to the exhaust manifold105, because the intake and exhaust valves 130, 150 are deactivated toCDA mode cylinders. This reduces the flow rate of the exhaust 420. Theexhaust 420 is more stagnant in the aftertreatment system, and so itlingers in catalyst 800 longer, thereby transferring more pollution andheat to the catalyst 800. A hot catalyst 800 is an efficient catalyst,as shown in the Example of FIG. 12. For a given mixture of catalystmaterials (Platinum, Palladium, Rhodium, etc.), the catalyst 800 has anideal operation temperature range. In this ideal temperature range, thecatalyst is the most efficient for capturing pollution. So, controllingthe temperature of the exhaust controls the temperature of the catalyst800, which controls the efficacy of the catalyst 800 to capturepollution. Moving in and out of CDA mode controls the exhausttemperature by adjusting the AFR in each cylinder. Additionallycontrolling the AFR via one or more of EGR valves, intake assistdevices, and fuel injection further impacts the exhaust temperature andpollution capture.

FIG. 12 shows one example of a catalyst 800. Adjusting the filtrationmaterials of the catalyst 800 will shift the illustrated line. For theexample, the catalyst 800 has a “bed” of material through which theexhaust 420 passes. The heat of that “bed” impacts the efficiency of thepollution capture. Nitric and Nitrous Oxides (NOx) is the targetpollutant of FIG. 12. Other pollutants, such as Sulphur or hydrocarbonscan be target pollutants, among others. At 100 degrees Centigrade, thecatalyst is 0% efficient to capture NOx (point A). At 150 degrees, thecatalyst converts only 24% NOx (point B). Raising the exhausttemperature to 200 degrees Centigrade (point C) brings NOx conversionefficiency up to 78%, with 90% efficiency at 250 degrees (point D) and96% efficiency at 300 degrees Centigrade (point E). For the examplecatalyst, it is therefore ideal to have an exhaust temperature near 300degrees Centigrade.

Material selection limits at what temperature the catalyst is efficient,at what temperature the catalyst is ruined via sintering effects, and atwhat temperature the catalyst can conduct diesel particular regeneration(DPR). Regeneration processes burn off pollutants at a high heat, whichlimits the pollutant's atmospheric entry and environmental pollution.Burning off the pollution renews the catalyst 800 to capture pollutionanew. FIG. 12 shows that at a regeneration temperature of 500 degreesCentigrade, the catalyst is only 50% efficient at capturing NOx.

In certain load modes for the engine system, exiting normal mode andentering CDA mode can raise exhaust temperature 100 degrees Centigrade.The impact can be seen by turning to FIG. 7. An engine can idle at aspeed dependent on the engine build, and the example of FIG. 7 shows anengine having a speed from 800 rotations per minute (RPM) to over 2400RPM. The example also uses an engine load from zero to 20 bar. Otherengine set-ups are contemplated, and can vary based on engineapplication and duty cycle. For example, a passenger bus can run at adifferent range of RPMs than a dump truck. The load at idle, such aswhen the bus adjusts during pick-up, can differ from the load at idlefor tipping the dumper of a dump truck. Since the CDA mode strategy canbe applied to a variety of light, medium duty, long haul and heavy dutyapplications, the example of FIG. 7 is not shown to restrict the claimsto a single range of RPMs versus load. FIG. 7 shows that the engine runsbelow the ideal catalyst bed temperature of 300 degrees Centigrade,shown in FIG. 12, for a significant operation range. Without sufficientload, the example engine does not generate enough heat to efficientlycapture NOx.

Off-highway vehicles, such as forklifts, graders, pavers, harvesters,mowers, construction equipment, farming equipment, etc. operate for asignificant amount of time at a load insufficient to heat the catalystto its ideal temperature. But, one cannot simply adjust the catalyst toa different material because the vehicles have excursions to highertemperatures, and thus the catalyst 800 need to withstand highertemperatures without damage.

The unloaded idle mode (point UI) can have a high tailpipe pollutionemission because the engine exhaust is far below the ideal catalysttemperature. Entering CDA mode to deactivate at least one cylinder addsinstant heat to the exhaust by increasing the fuel efficiency of theengine. By adjusting the AFR to the firing cylinders, an additional 100degrees Centigrade of heat can be instantly added to the exhaust.Recalling the curve of FIG. 12, the additional heat dramaticallyincreases the pollution filtration at unloaded idle. The example loadedidle mode (point LI) has a 200 degree Centigrade exhaust temperature.Adding 100 degrees to this would bring the catalyst efficiency near itspeak. Thus, adjusting the number of cylinders in CDA mode and adjustingthe fuel to the remaining firing cylinders permits pollution filtrationtailoring via thermal management of the catalyst 800.

The instant heat-up via CDA mode can be applied to diesel particulatefilter (DPF) regeneration techniques. Instead of idling a vehicle to runa DPF regeneration cycle, computer control can initiate CDA mode duringselect operation modes or at select operation times. Further tailoringof the AFR augments the heat added to the exhaust. And, point R, anideal DPF regeneration point, is more easily achieved without the use ofa fuel doser or idle cycle.

It is possible to implement a method for monitoring exhaust temperature,wherein the air fuel ratio to a firing cylinder is adjusted to raise theexhaust temperature or to maintain the exhaust temperature above athreshold temperature. It is possible to monitor a pollution levelexhausting from the diesel engine and to adjust the number of cylindersentering cylinder deactivation mode to reach a target pollution level.It is further possible to adjust the air fuel ratio to the at least onefiring cylinder based on reaching the target pollution level.

It is possible to monitor an exhaust flow rate through theaftertreatment system, and to adjust the number of cylinders enteringcylinder deactivation mode to reach a target exhaust flow rate.

FIG. 4A summarizes steps for entering cylinder deactivation. In stepS103, fuel is cut off to a selected cylinder. In step S105, intake andexhaust valves are disengaged from actuation, whether by electric orhydraulic means, such as e-solenoid, electric latch, hydraulic latch,cam selection, disabling a controllable lift mechanism, a cam-camlessactuator, a hybrid electro-hydraulic system, or like means. A quantityof intake flow is trapped in the deactivated cylinder and the example ofstep S107 of FIG. 4A traps a charge of air.

The method of FIG. 4A can be used alone to increase fuel efficiency andpollution control for an engine. But, FIG. 4B shows cylinderdeactivation combined with additional control benefits. In step S401,the control system 1400, which can be a dedicated on-board computer, asubsystem of the Electronic Control Unit (ECU), or other programmablecircuitry, decides whether the engine load meets criteria for enteringCDA mode. The computer control system 1400 can be as summarized in FIG.14, such that sensor data is collected from various sensors, includingintake manifold sensor 173, exhaust manifold sensor 175, and exhaustsensor 807 and sent along a BUS or like wiring to sensor data storage.

Memory device 1401 is a tangible readable memory structure, such as RAM,EPROM, mass storage device, removable media drive, DRAM, hard diskdrive, etc. Signals per se are excluded. The algorithms necessary forcarrying out the methods disclosed herein are stored in the memorydevice 1401 for execution by the processor 1403. When optional variablegeometry turbocharger control is implemented, the VGT control 1415 istransferred from the memory 1401 to the processor for execution, and thecomputer control system functions as a turbocharger controller.Likewise, the computer control system 1400 implements stored algorithmsfor EGR control 1414 to implement an EGR controller; implements storedalgorithms for intake assist device control 1416 to implement intakeassist controller; implements stored algorithms for fuel injectioncontrol 1413 to implement fuel injection controller. When implementingstored algorithms for VVA control 1412, various intake valve controllerand exhaust valve controller strategies are possible relating to valvetiming and valve lift strategies, as detailed elsewhere in thisapplication,

While the computer control system 1400 is illustrated as a centralizedcomponent with a single processor, the computer control system 1400 canbe distributed to have multiple processors, or allocation programming tocompartmentalize the processor 1403. Or, a distributed computer networkcan place a computer structure near one or more of the controlledstructures. The distributed computer network can communicate with acentralized computer control system or can network between distributedcomputer structures. For example, a computer structure can be near theturbocharger 501 for VGT control 500, another computer structure can benear the EGR valve 410 for EGR controller 400, another computerstructure can be near the intake and exhaust valves for variable valveactuator 200, yet another computer controller can be placed for fuelinjection controller 300, and yet another computer controller can beimplemented for intake assist controller 600. Subroutines can be storedat the distributed computer structures, with centralized or coreprocessing conducted at computer control system 1400.

If the engine system meets CDA criteria, as by having an appropriateload or crankshaft RPM, or both, the computer control system selects thenumber of cylinders that can be deactivated while meeting current loadand RPM requirements in step S403. Additional factors to consider areone or more of whether the exhaust temperature is within a thresholdrange or at a target temperature, whether the brake thermal efficiency(BTE) is above a BTE threshold, or whether the tailpipe emissions arewithin a range or at a target level. One strategy deactivates as manycylinders as possible without impacting the torque output of the engine.Another strategy deactivates as many cylinders as possible to maintainas high an exhaust temperature as possible. Another strategy deactivatesas many cylinders as possible to have as fuel-efficient operation aspossible.

Once the number of cylinders for deactivation are selected in step S403,the fuel injection controller 300 shuts off fuel to the selectedcylinders in step S405. A concurrent or consequent adjustment of airfuel ratio (AFR) to the firing cylinders can be made in step S413. Theamount of fuel injected in to the cylinders ranges from 0-100%, and iscomputer controllable by appropriate mechanisms, including sensors,transmitters, receivers, and actuators. Step S413 can additively oralternatively comprise adjusting one or more of the timing or quantityof fuel injection, intake flow, exhaust gas recirculation (EGR), valveopening or valve closing profile (lift or timing) for the firingcylinders. This can comprise the AFR tailoring strategies detailed aboveand can comprise compressor 512 or intake assist device 601 or excludeturbocharger 501 as appropriate.

With fuel adjustments made, the intake and exhaust valve actuation isshut off for the selected, deactivated, cylinders in step S407. Thesystem monitors one or more of exhaust temperature, brake thermalefficiency, pollution level, exhaust flow rate through the catalyst,etc. in step S409. If it is not possible to adjust the number ofdeactivated cylinders, the monitoring in step S409 continues, But, if itis possible to deactivate additional cylinders, step S411 determines todo so. For example, the thresholds for temperature, pollution or flowrate could indicate that an increase or decrease in the number ofcylinders in CDA would improve exhaust conditions. So, if the thresholdsindicate that adjusting cylinders in CDA mode would benefit the targetexhaust conditions, the method checks whether other parameters, such asload and RPMs, permit CDA mode by returning to step S401.

In one aspect, and returning to FIG. 5, an engine is generalized andlabelled with 6 cylinders in a linear fashion for convenience. Inpractical implementation, the cylinders are not always linearly aligned.Even when they are, they are not always fired in the sequence numberedin the Figures. That is, the cylinders may not fire in the sequence 1,2, 3, 4, 5, 6. For example, a firing sequence for an engine in normaloperation mode can be 1, 5, 3, 6, 2, 4. In CDA mode, cylinders 4, 5, 6are deactivated. The remaining cylinders fire in sequence 1, 3, 2.Depending upon where the engine is in its firing sequence, the cylindersselected for deactivation can change between algorithm iterations. So, afirst iteration can fire as explained. A second iteration could shiftthe normal firing sequence to 3, 6, 2, 4, 1, 5. In this sequence,cylinders fire 3, 2, 1, while cylinders 4-6 are deactivated. However,the start sequence for implementing a new CDA mode deactivation sequencecould activate deactivated cylinders, and deactivate firing cylinders. Asequence of 5, 3, 6, 2, 4, 1 would fire cylinders in sequence 5, 6, 4,with cylinders 1-3 deactivated. So, not only can the number of cylindersfiring and deactivated change, but the cylinders selected for firing anddeactivated can change between algorithm iterations.

Returning to the flow diagram, the results of step S409 can be analyzedand a determination can be made in step S415 to decide whether to adjustthe exhaust profile. As above, to adjust aspects of the exhaust and itsability to heat the catalyst 800 or have pollution filtered from it, itcan be necessary to adjust the engine activity at the cylinder level.And so, if the exhaust profile is to be adjusted, the algorithm returnsto step S413. Otherwise, the system continues to monitor as in stepS409.

It may be necessary to exit CDA mode altogether, in step S417, as whenthe load on the engine increases above a threshold. Or, as when thebrake thermal efficiency or pollution control is better outside of CDAmode. The system checks whether the engine still meets criteria forimplementing CDA mode by returning to step S401. If base criteria arenot met, step S417 triggers an exit from CDA mode. The deactivatedcylinders receive valve actuation control and fuel injection to returnto firing mode. However, the algorithm can continue to check whether AFRadjustments or valve profile adjustments benefit the exhaust profile, asby continuing the flow through steps S413, S409, & S415.

Triggering conditions for entering or exiting CDA mode, or for combiningvariable valve actuation techniques with normal or CDA mode cylinders,are outlined in FIGS. 7-13. Pollution management is interrelated withAFR and exhaust temperature, and so one triggering condition can impactother triggering conditions. Adjusting one aspect of engine operationcan impact more than one threshold range for triggering conditions.

A bold line in FIG. 7 indicates a target temperature for a givencatalyst bed composition. Below the bold line, a threshold range for anexhaust temperature range triggers an indication that CDA mode isappropriate for raising exhaust temperature. When the system determinesexhaust temperature is below the target temperature, the control system1400 emits commands to enter CDA, commensurate with otherconsiderations, such as load and RPM requirements. Above the bold line,it is possible to exit CDA mode in favor of other techniques outlined inFIG. 8.

The threshold range can comprise an exhaust temperature range below anideal catalyst bed temperature. The ideal catalyst bed temperature canbe between 200-300 degrees Centigrade, above 200 degrees Centigrade,above 300 degrees Centigrade, or can be an exhaust temperature beneath adiesel particulate filter regeneration temperature. In this lastinstance, the diesel particulate filter regeneration temperature can bearound or above 500 degrees Centigrade. Outside the temperaturethreshold range, it is possible to exit CDA mode.

An exhaust temperature sensor 807 in combination with the control system1400 can receive and process exhaust temperature data from the exhausttemperature sensor. Based on the exhaust temperature data, commands canbe adjusted to the fuel injector to adjust the quantity of fuel injectedto active combustion cylinders of the plurality of combustion cylinders.Also, commands can adjust the number of combustion cylinders selectedfor deactivation.

Turning to FIG. 8, one implementation strategy is shown for triggeringvarious operation modes for the engine. Similar to FIG. 7, the controlsystem 1400 can enter CDA mode whenever the load on the engine is belowa first load threshold LT1. CDA mode can be entered across the entireengine speed operating range, in rotations per minute (RPM), from anidle mode up to a maximum engine crankshaft rotations per minute. Zone 1comprises idle, low load, and loaded idle modes. CDA mode can be usedalone or with EGR boosting, so as to lower the AFR and raise exhausttemperature. Optimizing fuel use in the firing cylinders, as byadjusting fuel injection, permits optimal fuel efficiency and high heatexhaust. Reducing cylinders in use reduces flow rate, and so thecatalyst can reach points C, D, & E in FIG. 12 despite being inhistorically problematic Zone 1. Exhaust temperatures are traditionallytoo low to trap particulates in Zone 1, but the CDA mode techniquesdescribed herein increase catalyst activity. While the efficient fueluse increases NOx output in the exhaust, the pollution is moreefficiently captured in the catalyst 800.

The triggering conditions of FIG. 13 indicate that as the NOx conversionefficiency of the catalyst increases with the catalyst bed temperaturereference, the permissible amount of NOx in the exhaust can increase.Pollution regulations require that engines meet an upper limit 0.2g/hp-hr (0.2 grams per horsepower hour) NOx emission, or 0.3 g/hp-hr NOxemission, as measured at the tailpipe. The engine can emit (engine-out)NOx over the course of an hour, and the totality of the NOx emissioncannot be above the upper limits (NOx pollution thresholds) at thetailpipe of the engine exhaust system. The engine can emit more than theupper limit, but by the time the exhaust reaches the tailpipe, the NOxlevel must be reduced below the pollution threshold.

The catalyst 800, when 96% efficient, can receive exhaust having 5.0grams per horsepower hour NOx and remove enough NOx to stay under the0.2 g/hp-hr upper limit. Likewise, when the catalyst is 96% efficient,the catalyst can receive 7.5 g/hp-hr NOx from the exhaust manifold, yetfilter pollution to stay under the 0.3 g/hp-hr upper limit. The amountof NOx pollution from the engine that can be filtered decreases as thecatalyst efficiency decreases. So, by using the catalyst temperature asa determinative threshold, and maintaining the catalyst temperaturewithin a target threshold range, or at a target temperature, the firingcylinders can be run in high fuel efficiency mode (high temperature,high NOx output) without increasing pollution at the tailpipe. Thealgorithm of FIG. 4B can include in steps S415 and S411, processes tomanage pollution at the tailpipe. The results of the monitoring stepS409 can be processes to ensure that the NOx for the horsepower-hourdoes not exceed the pollution threshold, as by adjusting fuelefficiency, exhaust temperature, fuel injection, intake flow, number ofcylinders in CDA mode, etc. Low NOx modes, such as a lower fuelefficiency mode, can be selected over higher NOx modes to ensure thatthe tailpipe emission pollution threshold is met for the requisite timeframe. For example, when the catalyst bed temperature is in an idealrange, it is possible to suspend CDA mode, or to decrease fuelefficiency to reduce the amount of NOx exiting the engine. There is thenless NOx for the catalyst to filter, and more pollution is trapped inthe catalyst. Thus, the control algorithm is configured to processespollution level data to iteratively adjust the commands to one or moreof the fuel injector 310, intake assist device 601, VGT turbocharger501, EGR valves 412, 414, or 410, or valve actuators until the pollutionlevel is below the pollution threshold.

Returning to FIG. 8, Zone 2 indicates a second load threshold LT2. Amedium load, such as a 50% load mode, can be the second load thresholdLT2. In zone 2, CDA can be used across the engine speed operating range.Intake assist device 601 can boost AFR to meet torque outputrequirements for the engine.

A load monitoring sensor such as crankshaft sensor 107 can determine aload on the engine. The control algorithm can receive load data from thecrankshaft sensor 107 and determine a load on the engine. The controlsystem 1400 can determine an engine output requirement based on the loadon the engine. When a load on the engine is below a first load thresholdLT1, the control system 1400 can adjust the number of the plurality ofcombustion cylinders selected for deactivation to meet engine outputrequirements. When a load on the engine is above the first loadthreshold LT1, the control algorithm is configured to boost intake flowto the intake manifold. When the load on the engine is above a secondload threshold LT2, the control algorithm exits CDA mode.

The load on the engine can impact the decision to enter CDA mode in avariety of ways. Comparing FIGS. 8 & 9 illustrates this. FIG. 8 breaksthe load versus RPM in to Zones 1-4 with load thresholds LT1 & LT2. FIG.9 correlates load to one example of the number of cylinders deactivatedin CDA mode. Above second load threshold LT2, CDA mode is not used. Theengine requires more torque output than can be provided in CDA mode. Allcylinders are firing to accommodate the load.

The control system 1400 can monitor the engine operating mode. Athreshold range for entering CDA mode can comprise one or more of anidle engine operating mode threshold LTA, a loaded idle engine operatingmode threshold LTB, and a loaded engine operating mode threshold LTC.The number of cylinders of the multiple-cylinder diesel engine enteringcylinder deactivation mode is adjusted based on whether the engineoperating mode is the idle engine operating mode, the loaded idle engineoperating mode, or the loaded engine operating mode. FIG. 9 shows oneexample of the load thresholds versus number of cylinders deactivated.While even numbers of cylinders are shown, other numbers, such as oddnumbers or single-digit numbers of cylinders can be selected fordeactivation.

Engine operating modes can comprise a lightly loaded mode, a medium loadmode, and a heavy duty load mode, and the threshold range for enteringCDA can comprise the lightly loaded mode and the medium load mode. Anengine operating mode can also comprise a start-up mode, and thethreshold range for entering CDA can comprise the start-up mode.

Determining whether to enter CDA can comprise monitoring an enginecrankshaft speed via crankshaft sensor 107. When a threshold rangecomprises a high speed threshold range above ST and a low speedthreshold range below ST, the number of cylinders entering cylinderdeactivation mode is adjusted based on whether the engine crankshaftspeed is within the high speed threshold range of the low speedthreshold range.

A normal operating mode can be used in Zone 4, especially when an engineis optimized for operation in Zone 4, such as a cruising mode. Anaugmented mode can be used in Zones 1-3, in Zones 2 & 3 only, or in Zone3 only. The augmented mode applies the principles of steps S409, S415, &S413 to adjust the valve opening or valve closing profile to impact fuelefficiency. Above threshold speed ST, Zone 3 is used. Below thresholdspeed ST, Zone 4 techniques are used.

The techniques of the augmented mode can adjust the valve profiles, assummarized in FIG. 15. Each valve can have its lift height adjusted andtime it is open adjusted. The example of FIG. 15 shows an early closingprofile in combination with a low lift in profile LL. A normal lift andnormal opening and closing profile LN is also shown. A late valveclosing with a high lift profile LH is shown. Other valve profiles arepossible, so FIG. 15 is exemplary and not restrictive of the range ofprofiles possible on the intake and exhaust valves. The lift and thetiming of intake or exhaust valve opening or closing can be tailored tothe engine operating conditions. As outlined above for the variablevalve actuator (VVA) 200, augmented mode techniques can comprise EarlyIntake Valve Opening (EIVO), Early Intake Valve Closing (EIVC), LateIntake Valve Opening (LIVO), Late Intake Valve Closing (LIVC), EarlyExhaust Valve Opening (EEVO), Early Exhaust Valve Closing (EEVC), LateExhaust Valve Opening (LEVO), Late Exhaust Valve Closing (LEVC), acombination of intake valve actuation timing and exhaust valve actuationtiming, such as EEVC and LIVO adjusts (Negative Valve Overlap (NVO)).The one technique for operating the engine system comprises exitingcylinder deactivation mode when the diesel engine system is operatingoutside a threshold range, such as second load threshold LT2, andentering an early intake valve closing mode. Another technique exitscylinder deactivation mode when the diesel engine system is operatingoutside a threshold range, such as second load threshold LT2, andentering a late intake valve closing mode.

Cylinder deactivation requires an implementation strategy for optimaltrade-offs between BSFC (Brake Specific Fuel Consumption) & NOx & TOT(turbine out temperature). Early Intake Valve Closing (EIVC) and LateIntake Valve Closing (LIVC) yield good BSFC. It is possible to use thesetechniques at high speed and high load conditions. While NOx is higherfor EIVC and LIVC, the catalyst is heated to an ideal filtering rangevia the CDA at start-up and low load. The catalyst can filter theincreased NOx for a net tailpipe emission within the desired regulatorylimits.

As FIG. 10 shows, the brake thermal efficiency (BTE) of the engineincreases as the load increases. The scale for the load differs fromFIG. 7. FIG. 7 shows an example load in bars (pressure). But FIG. 10shows load in a percentage relative to the engine's load capacity. So,the engine has a load range from 0-100% of its capacity. The BTEincreases the closer the engine gets to its maximum load capacity. TheBTE can be a triggering condition for entering or exiting CDA mode. Aload below a threshold BTE triggers entry in to CDA mode for a thresholdrange of BTE values. Above the BTE threshold, the engine system exitsCDA mode to take advantage of high load, high BTE efficiency operatingconditions. FIG. 16D contrasts brake thermal efficiency (BTE) betweennormal all cylinders-firing mode (triangles) and CDA mode (circles) foran example 6-cylinder engine. In FIG. 16D, CDA mode outperforms normaloperation mode under a threshold. Reducing the number of firingcylinders increases BTE for the example engine system when the load isless than 200 foot-pounds of torque. Above 200 ft-lbs torque, it isbeneficial to use normal operation with all cylinders firing.

FIG. 7 correlates the high load condition against the exhausttemperature to show that the catalyst bed is working efficiently formuch of the high load output of the engine. Catalyst bed temperature ishigh enough to capture pollution, and so monitoring BTE and regulatingCDA mode based on BTE impacts the temperature of the catalyst and theengine system's ability to regulate pollution. Monitoring a brakethermal efficiency permits steps for adjusting the air fuel ratio to afiring cylinder based on maintaining the brake thermal efficiency abovea brake thermal efficiency threshold. CDA mode can bring the BTE up tothe threshold for lower loads, and when a load threshold is crossed, CDAmode is exited in favor of firing all cylinders.

Other triggering events for entering or exiting CDA mode can includemonitoring an accelerator position, and wherein the threshold rangecomprises a subset of accelerator positions. A certain rate ofacceleration causes a load on the engine, and so CDA mode can be linkedto the accelerator as it can be linked to the load. Other user inputs,such as buttons, levers and other user inputs can trigger a thresholdrange for entering CDA mode. For example, the user can select DPFregeneration mode, which causes the engine system to enter CDA to reacha target DPF regeneration temperature, such as point R in FIG. 12, oranother target temperature suitable for the catalyst contents.

Exiting CDA mode can comprise deselecting the combustion cylindersselected for deactivation, commanding the injection controller toactivate the respective fuel injector for the at least one of thedeselected combustion cylinders, commanding the intake valve controllerto activate the respective intake valve for the at least one of thedeselected combustion cylinders, and commanding the exhaust valvecontroller to activate the respective exhaust valve controller for theat least one of the deselected combustion cylinders. The controlalgorithm is further configured to adjust commands to the fuel injectorto adjust the quantity of fuel injected to active combustion cylindersof the plurality of combustion cylinders based on the engine outputrequirement. As the cylinders exit CDA mode, the fuel injector 310 iscontrolled to redistribute fuel based on engine load requirements.

The control algorithm can comprise instructions to receive air flow datafrom an air flow sensor such as intake manifold sensor 173. The controlsystem 1400 can determine an air flow amount to respective intakevalves, determine an air fuel ratio for each of the plurality ofcombustion cylinders based on the determined air flow amount and basedon the fuel injector commands, and, based on the determined air fuelratio, command the intake assisting device to increase air flow to theplurality of combustion cylinders when the load on the engine is withina predetermined range. Based on the determined air fuel ratio, thecontrol system can adjust commands to the fuel injector 310 to adjustthe quantity of fuel injected to active combustion cylinders of theplurality of combustion cylinders.

Returning to FIG. 8, Zone 2, in a normal low load condition, the air tofuel ratio (AFR) can be 80 parts air to one part fuel (80:1). In a CDAmode, the AFR cuts in half, which increases the heat of combustion. Amedium load can have an AFR of 40:1. Lowering the AFR increases thetemperature of the exhaust (TOT or turbine out temperature), which canbenefit the ability of the catalyst to collect undesirable emissions.But, going to or below 20:1 AFR increases exhaust emissions and is notdesired. So simply entering CDA on half of the cylinders in a mediumload could generate too much soot. It is beneficial to run an intake airassist device during CDA mode to more effectively regulate the AFR. Thebenefit of running the intake assist device 601 outweighs the detrimentof any increased load on the engine 100 to power the intake assistdevice 601, as by pulley operated devices. Deactivating half of thecylinders can achieve a high temperature TOT benefit for the exhaust inmedium load conditions when the AFR is boosted above the low 20:1 AFRthat would occur without intake flow assistance. Without the intake flowassist, using CDA in a medium load would generate soot in the exhaust.Using the intake assist device extends the benefit of CDA mode beyondlow load and idle conditions and gives fuel economy benefits despite thedrain of powering the intake assist device 601. This is because theexhaust output is reduced when shutting off cylinders and when reducingfuel use. The amount of exhaust output during CDA mode is insufficientto excite the turbocharger enough to boost the intake flow to adesirable AFR.

The air assisting device acts to supply fresh air in lieu of, or tosupplement, the air supplied via turbocharging to raise the ratio ofoxygen to fuel. Instead of using CDA only at very low load or idleconditions, CDA use is extended to higher load conditions. The airassisting device is used to raise the air fuel ratio (AFR) from 20:1 to23:1 or 24:1. For example, using an air pump permits CDA at 25-35% load.A larger range is 25-50% load. This allows a diesel engine to benefitfrom reduced emissions over a larger operating range and at loads whereturbocharging otherwise wouldn't suffice to raise the AFR. The low fueluse and low emissions is possible over a greater engine operating rangebecause the oxygenating source is not dependent on the turbocharger. Theintake assist device 601 can be an air pump, a supercharger or even afan.

Because the duty cycle of the intake air assisting device is very small,for example, 2%, and because the intake air assisting device size iskept very small, for example, 15% the size of the engine or less, thereis a net fuel savings. For example, a 15 L, 7 L, or 2 L engine can bepaired with a 0.3 L supercharger, a fan, or an air pump. Using an 2 Lengine again as an example, the intake air assisting device suppliesapproximately 0.5 kg/min air flow or less to increase the AFR for the25-50% load operation. The low, 140-150 kPA intake manifold pressure inthis load range permits a low capacity intake air assisting device andresults in a low power use.

CDA mode can be used on a six cylinder engine or an eight cylinderengine. CDA can be entered on half of the cylinders, two of thecylinders, etc. The engines can operate with only two firing cylinders.The use of CDA mode creates “an engine within an engine,” because agreat capacity can be installed on a device or vehicle for high loadoperation, but computer control strategies reduce the engine fuel useand pollution to that of a much smaller engine for small loads and idleconditions. That is, CDA mode can be used to selectively reduce theengine displacement. But, CDA can also be used to double the load percylinder, increasing torque output from each cylinder over a normalmode. These assets can reduce emissions, improve fuel economy, andincrease TOT.

Yet another benefit of CDA mode is the ability to recover energy ofcompression. Because charge air or other intake flow is captured in aCDA cylinder, and because the piston 160 is not deactivated, the pistoncontinues to cycle up and down in the deactivated cylinder. The pistonfollows its stroke cycle, and work is done to compress the charge ofair. But the piston springs back, which can augment torque output fromthe diesel engine by coupling compression spring-back from the piston160 to the crankshaft 101. This “air spring” effect can return moreenergy to the crankshaft than friction losses would otherwise rob from anormal mode-activating cylinder. Using CDA mode puts less wear on theengine than engine braking, regular combustion, positive power, orbraking loads. Shutting off cylinders preserves them, and running theremaining firing cylinders efficiently is less wear across the enginethan running all cylinders inefficiently. To augment the spring-back, itis possible to boost the intake flow to the cylinder prior todeactivating the valves.

NOx Adjustment Strategies Using CDA

A fuel efficient combustion cycle has increased NOx emission. Consumerswant good fuel economy, but Federal Regulations require low NOx output.The goals are at odds.

One compromise has been to make the engine less fuel efficient to reduceNOx output, as by adjusting engine timing to retard the engine, or as byexhaust gas recirculation (EGR). Redesigning other system componentsattempts to increase fuel economy to make up for the loss of fuelefficiency. The other components make up for fuel economy losses in theengine by being more aerodynamic, having less drag, etc. But, in theend, the engine is fuel inefficient.

One issue is that a fuel-efficient diesel (one having low BSFC—brakespecific fuel consumption) has increased NOx output. For example, a fuelefficient diesel can output 6-9 grams NOx/engine hour. However,regulations require output of 0.2, and soon to be 0.02 grams NOx/enginehour. Only by having an efficient aftertreatment system can the goal bereached while satisfying consumer demand for fuel efficiency. And so itbecomes necessary to heat the catalyst quickly for efficient filtering.

For example, being 8% more fuel-efficient, as measured by BSFC,increases NOx 2 g/hp-hr. Another 8% fuel efficiency increase does thesame, and so fuel efficiency/fuel economy can increase 16%, but at acost of moving from 1 g/HP hr to 5 g/Hp hr NOx. If the catalyst can stayin its most efficient filtering range, the NOx is captured, and thetailpipe emission meets the necessary standards.

In a gasoline engine, CDA would work to reduce pumping losses, and toreduce need for an intake throttle. The benefits would be limited toflow and drag losses. A gasoline engine must be run stoichiometricfuel:air (AFR), and so CDA mode's benefits are more limited.

On a diesel engine, which lacks a throttle, CDA is less about pumpinglosses, and more about efficient combustion. The diesel engine can havea range of air-fuel ratios. The AFR can be adjusted to conditions, andso CDA works to run each cylinder at a higher load, which increases thatcylinder's brake thermal efficiency, which improves fuel economy. CDApermits fuel economy benefits by deactivating one or more cylinders toconserve fuel to that cylinder and to conserve energy expenditures toactuate that cylinder. Fuel economy is increased in the remaining activecylinders, because the fuel to those cylinders is adjusted in responseto the deactivated cylinder and in response to the load or idleconditions. The amount of fuel can be metered for the circumstances.

Pollution is reduced in one aspect by deactivating cylinders in CDAmode. Turning off one or more cylinders causes reduction in inefficientfuel use, which lowers pollution and fuel consumption. So, CDA causesinstantaneous benefits. Because the AFR is adjusted to the activecylinders, the amount of air necessary for optimal combustion is alsotailored to the active cylinder. In a low load condition, the amount oftorque output needed is quite small. Pushing air in to all cylinders,and pushing fuel in to all cylinders puts out too much torque and usestoo much energy and fuel. Deactivating one or more cylinders permits oneor more remaining firing cylinders to use more fuel or less air,resulting in a hotter combustion. The higher heat combustion has lowertailpipe pollution because the catalyst bed can be heated and pollutioncan be better filtered. In one aspect, the NOx emissions reduce becauseless quantity of exhaust output generates less NOx. However, higher fueleconomy increases NOx, because efficient combustion increases NOx. Thus,there are tradeoffs between increased fuel efficiency, decreased exhaustamount, and the ability of the catalyst to heat to optimum NOx filteringtemperature.

Just using CDA, absent adjustments to AFR or fuel to other cylinders,increases the fuel efficiency by 5%, because there is less fuel use withcylinders deactivated. Friction losses to the CDA piston are faroutweighed by gains from not running the valves and injector(s).

But, adjusting AFR to the active cylinders can increase pollution byincreasing the efficiency of combustion. Efficient fuel use in acylinder can increase NOx. So with CDA, the amount of air necessary foroptimal combustion is also tailored to the active cylinder. In a lowload condition, the amount of torque output needed is quite small.Pushing air in to all cylinders, and pushing fuel in to all cylindersputs out too much torque and uses too much energy and fuel. Deactivatingone or more cylinders permits one or more remaining cylinders to usemore fuel or less air, resulting in a hotter combustion. The higher heatcombustion has lower pollution because the catalyst bed can be heatedand pollution can be better filtered by the aftertreatment system, whichruns most efficiently when heated to between 200-300 Degrees Centigrade.

Adjusting the AFR with CDA instantly heats the exhaust. The higher heatexhaust warms the catalyst to its optimum filtering temperature. UsingCDA, it is possible to remove the fuel doser that would otherwise beneeded to raise exhaust temperature during low load or low temperatureoperation. This reduces aftertreatment fuel use and expenses. For ureapollution management systems, the need for urea is dramatically reduced.

On the one hand, NOx emissions reduce during CDA in low load conditionsbecause there is a decrease in the amount of exhaust gas output. Fewercylinders in use spew less exhaust. Less exhaust output generates lessNOx. However, decreasing the exhaust via CDA reduces flow rate by half,which reduces the amount of exhaust for heating the catalyst. But, thereduced flow rate retains heat in the catalyst better, and the exhaustis hotter, which heats the catalyst quicker. However, higher fueleconomy increases NOx, because efficient combustion increases NOx. Withbetter catalyst heating, the catalyst is better able to absorb the NOx.Thus, there are tradeoffs between increased fuel efficiency, decreasedexhaust amount, and the ability of the catalyst to heat to optimum NOxfiltering temperature.

The exhaust heats instantly, because CDA can be turned on and off in onecam revolution, but the surrounding metal, such as cylinder-to-cylinderheat transfer and such as the catalyst itself, take longer to warm upfrom heat transfer. Meeting future emissions standards becomes an issueof heating the operating environment around the ideally heated exhaust.

Running the engine efficiently using CDA uses fuel more efficiently inthe active firing cylinders, while using no fuel in the inactivecylinders. The reduced fuel use increases fuel economy, which is highlydesired. The increased catalyst function versus low fuel use is alsohighly desired. Using less fuel more efficiently ultimately reduces NOxemissions for the engine.

Cylinder Deactivation Use Strategy (Exhaust Temperature On-Demand)

Cylinder deactivation is extremely beneficial to fuel economy andaftertreatment pollution management and can be implemented when the fullengine torque output is not required. CDA can be used to heat exhausttemperature, which heats the catalyst, which causes better NOxmanagement. A heated catalyst is better able to filter NOx.

CDA deactivates the intake valve, exhaust valve, and fuel injection to acylinder, while increasing the torque output of the remaining cylinders,as by running the other cylinders in a more fueled condition, or in amore stoichiometric air-fuel ratio. Unlike a gasoline engine, a dieselengine can have variations in the air-fuel ratio (AFR) such that theamount of air can be varied with respect to the amount of fuel to adjustthe torque output. Adjusting the AFR to adjust the torque output alsoadjusts the heat output of the cylinder.

One control technique implements CDA mode only when the exhausttemperature is below 250 degrees Centigrade. Below this temperature, NOxis poorly filtered. Above this temperature, the catalyst is efficient.Fuel economy ordinarily closely tracks this phenomenon. But, CDAincreases fuel economy by more efficiently using fuel in each cylinder,as by adjusting the air-fuel ratio (AFR).

In diesel, a fuel efficient cylinder increases both NOx output andexhaust temperature. So, it is thought that CDA is bad: it increasesNOx. But, the temperature increase improves the ability of the catalystto filter pollution. This ultimately filters more NOx than the fueleconomy increase adds, resulting in a net reduction in pollution.

Note that the 250 degree line for implementing CDA can be adjusted to200 or 300 degrees Centigrade, depending upon catalyst material and goalNOx output.

A large portion of a diesel engine's operation map outputs torque withthe exhaust temperature below 250 Centigrade as shown in FIG. 7. So inlow load or idle conditions, the engine speed can reach 2400 RPMswithout outputting enough heat to efficiently use the aftertreatmentsystem. CDA can thus be implemented across a large range of engine RPMsto raise exhaust temperature for efficient NOx filtering. Contrary toprior thought, CDA does not have to be limited to low engine speedoperation. CDA can be implemented based on exhaust temperature. Sincefull engine load capacity is not needed in the critical temperatureband, cylinders can be deactivated to meet aftertreatment temperaturegoals without impacting the operation speed of the engine. Thus, thecontrol strategy of implementing CDA only when the exhaust temperatureis below a certain temperature limit removes the reliance on engine loadfor determining CDA mode. The temperature limit controls the amount oftime CDA is active without impacting other load operation modes.

Studying the engine map reveals that the need for CDA mode decreases asengine RPMs increase. The engine is more able to output exhaust attarget aftertreatment temperatures as load and speed increase.Restricting CDA by temperature makes CDA use less detectable to thedriver, who has ordinary operation experience above the low-loadtemperature band.

Cylinder Deactivation for Catalyst Regeneration

It is difficult to design the catalyst for optimal operation for thefull temperature range of 0-600 degrees Centigrade. At some point, thelow temperature NOx filtering materials cannot withstand the heat of DPFcatalyst regeneration, yet higher temperature filtering materialsperform poorly at low temperatures. So, capturing NOx is difficult.

Using CDA, it is possible to remove the fuel doser that would otherwisebe needed to raise exhaust temperature during low load or lowtemperature operation. This reduces aftertreatment fuel use andexpenses. For urea pollution management systems, the need for urea isdramatically reduced.

One issue is that a fuel-efficient diesel has increased NOx output. Forexample, a fuel efficient combustion diesel can output 6-9 gramsNOx/engine hour. However, regulations require output of 0.2, and soon tobe 0.02 grams NOx/engine hour. Only by having an efficientaftertreatment system can the goal be reached while satisfying consumerdemand for fuel efficiency. And so it becomes necessary to heat thecatalyst quickly for efficient filtering and for efficient burn-off.

The exhaust heats instantly, for example, an additional 100-110 degreesCentigrade can be added to the exhaust temperature by switching fromnormal operation to CDA operation. This contrasts sharply with EEVO andother prior art strategies that must cycle for some time to bringexhaust temperature up. Current heavy machinery can take all 20 minutesof its FTP (Federal Testing Procedure) emissions test to come up to thecorrect temperature for emissions standards, if at all. Certainmachinery never generates enough heat to pass emissions tests. Otherstrategies require 7 minutes to warm up to reach emissions test. CDAmode can heat an aftertreatment system within 3 minutes. The increasedexhaust temperature available through CDA mode is greater than competingstrategies, and requires less fuel to reach that temperature thancompeting strategies.

Because CDA can be turned on and off in one cam revolution, the abilityto switch cylinders between normal and CDA modes permits fast tailoringof the exhaust temperature. Meeting future emissions standards becomesan issue of ideally heated and filtered exhaust.

Catalyst regeneration heats the catalyst to a particular temperature,for example 500-600 degrees Centigrade. NOx is burnt off, along withother pollutants, to clean the catalyst so that it can filter pollutiononce again. Because CDA can so instantly heat the exhaust, it is anasset for particulate filter regeneration techniques. Using CDA canreduce vehicle down time for regeneration, and provide more on-demandregeneration. So, instead of pulling road-side to run the engine at highRPMs with the parking brake on, CDA mode can activate during vehicleoperation to regenerate the catalyst.

Using CDA, it is possible to remove the fuel doser that would otherwisebe needed to clean the catalyst during low load or low temperatureoperation. This furthers the goal of redesign of the aftertreatment forone temperature band for efficient operation. Ideally, the catalystoperates from 200-600 degrees Centigrade, but from a materials scienceperspective, it is difficult to design the catalyst for the wholetemperature operating range 0-600 C. Thus, using CDA to instantly heatthe exhaust to 200 or more degrees Centigrade alleviates some of thematerial burden of including a low temperature filtering material in thecatalyst. The optimal temperature band of the aftertreatment can bemoved, and the materials within adjusted accordingly.

Other implementations will be apparent to those skilled in the art fromconsideration of the specification and practice of the examplesdisclosed herein. It is intended that the specification and examples beconsidered as exemplary only, with a true scope of the invention beingindicated by the following claims.

1-106. (canceled)
 107. A diesel engine system comprising: a plurality ofcombustion cylinders, each comprising an intake fuel injector, an intakevalve, and an exhaust valve; a catalyst for filtering pollution from anexhaust stream; a sensor configured to monitor at least one parameterindicative of a condition of the exhaust stream; a controller configuredto iteratively: receive the at least one parameter from the sensor; andwhen the at least one parameter meets a predetermined criterion forcylinder deactivation, deactivate the intake fuel injector, the intakevalve, and the exhaust valve of at least one of the plurality ofcombustion cylinders, such that the plurality of combustion cylinderscomprise one or more deactivated combustion cylinders and one or moreactive combustion cylinders, and adjust the air to fuel ratio in theactive combustion cylinders to increase the temperature of the exhauststream in the catalyst to a target temperature of about 200˜500° C. 108.The diesel engine system of claim 107, wherein the target temperature isabout 250˜300° C.
 109. The diesel engine system of claim 107, whereinthe air to fuel ratio in the active combustion cylinders is from 22:1 to24:1.
 110. The diesel engine system of claim 107, wherein the controlleris configured to determine an engine output requirement based on anengine load and to adjust the number of combustion cylinders fordeactivation to meet the engine output requirement.
 111. The dieselengine system of claim 107, wherein the sensor comprises a pollutionsensor configured to measure a pollution level in the exhaust stream,and wherein the at least one parameter comprises the pollution level.112. The diesel engine system of claim 111, wherein the predeterminedcriterion comprises the pollution level in the exhaust stream exceedinga pollution threshold.
 113. The diesel engine system of claim 112,wherein the controller is configured to select the at least one of theplurality of combustion cylinders for deactivation when the pollutionlevel in the exhaust stream exceeds the pollution threshold.
 114. Thediesel engine system of claim 111, wherein the pollution sensor isconfigured to monitor a mono-nitrogen oxide level in the exhaust stream.115. The diesel engine system of claim 111, wherein the controller isconfigured to process the pollution level measured in the pollutionsensor to iteratively adjust the air to fuel ratio until the pollutionlevel is below the pollution threshold.
 116. The diesel engine system ofclaim 107, wherein the sensor comprises a temperature sensor configuredto measure an exhaust temperature, and the at least one parametercomprises the exhaust temperature of the exhaust stream.
 117. The dieselengine system of claim 116, wherein the controller is configured toreceive the measured exhaust temperature from the temperature sensorand, based on the exhaust temperature, iteratively adjust the quantityof fuel injected to the active combustion cylinders and adjust thenumber of combustion cylinders for deactivation.
 118. A diesel enginesystem comprising: a plurality of combustion cylinders, each comprisingan intake fuel injector, an intake valve, and an exhaust valve; a loadsensor configured to monitor an engine load; a controller configured toiteratively: receive the engine load from the load sensor; determinewhether the engine load meets criteria for cylinder deactivation; whenthe engine load meets criteria for cylinder deactivation, select anumber of combustion cylinders for deactivation and deactivate theselected number of combustion cylinders by deactivating the intake fuelinjector, the intake valve, and the exhaust valve of the selected numberof combustion cylinders; monitor at least one parameter indicative ofthe engine condition; determine if the at least one parameter meets athreshold for adjusting the number of cylinders for deactivation; andcontinue monitoring the at least one parameter until the at least oneparameter meets the threshold for adjusting the number of cylinders fordeactivation.
 119. The diesel engine system of claim 118, wherein the atleast one parameter comprises one or more of an exhaust temperature, abrake thermal efficiency, a pollution level, and an exhaust flow rate ofthe exhaust stream.
 120. The diesel engine system of claim 118, whereinthe at least one parameter comprises an exhaust temperature, and thecontroller is configured to determine whether the exhaust temperature iswithin a threshold range or at a target temperature.
 121. The dieselengine system of claim 118, wherein the at least one parameter comprisesa brake thermal efficiency, and the controller is configured todetermine whether the brake thermal efficiency is above a brake thermalefficiency threshold.
 122. The diesel engine system of claim 118,wherein the at least one parameter comprises a pollution level, and thecontroller is configured to determine whether the pollution level iswithin a threshold range or at a target level.
 123. The diesel enginesystem of claim 118, wherein the controller is configured to adjust airto fuel ratio to the active combustion cylinders.
 124. The diesel enginesystem of claim 118, wherein the controller is configured to adjust oneor more of the timing or quantity of fuel injection, intake flow,exhaust gas recirculation, valve opening or valve closing profile forthe active combustion cylinders.
 125. A method of operating a dieselengine system, comprising: monitoring at least one parameter indicativeof a condition of an exhaust stream of an engine having a plurality ofcombustion cylinders; determining whether the at least one parametermeets a predetermined criterion for cylinder deactivation; when the atleast one parameter meets the predetermined criterion, selecting atleast one of the plurality of combustion cylinders for deactivation anddeactivating an intake fuel injector, an intake valve, and an exhaustvalve of the selected at least one combustion cylinder, such that theplurality of combustion cylinders comprise one or more deactivatedcombustion cylinders and one or more active combustion cylinders; andadjusting the air to fuel ratio in the active combustion cylinders toincrease the temperature of the exhaust stream to a target temperatureof about 200˜500° C.
 126. The method of claim 125, wherein the targettemperature is about 250˜300° C.
 127. The method of claim 125, whereinthe air to fuel ratio in the active combustion cylinders is from 22:1 to24:1.
 128. The method of claim 125, further comprising determining anengine output requirement based on a load of the engine and adjustingthe number of combustion cylinders for deactivation to meet the engineoutput requirement.
 129. The method of claim 125, further comprisingmonitoring a pollution level in the exhaust stream, wherein the at leastone parameter comprises the pollution level.
 130. The method of claim129, wherein the predetermined criterion comprises the pollution levelin the exhaust stream exceeding a pollution threshold.
 131. The methodof claim 130, further comprising selecting the at least one of theplurality of combustion cylinders for deactivation when the pollutionlevel in the exhaust stream exceeds the pollution threshold.
 132. Themethod of claim 129, wherein measuring the pollution level comprisesmonitoring a mono-nitrogen oxide level in the exhaust stream.
 133. Themethod of claim 129, further comprising processing the pollution levelto iteratively adjust the air to fuel ratio until the pollution level isbelow the pollution threshold.
 134. The method of claim 125, furthercomprising monitoring an exhaust temperature in the exhaust stream,wherein the at least one parameter comprises the exhaust temperature ofthe exhaust stream.
 135. The method of claim 134, further comprising,based on the exhaust temperature, iteratively adjusting the quantity offuel injected to the active combustion cylinders and adjusting thenumber of combustion cylinders for deactivation.
 136. A method ofoperating a diesel engine system, comprising: monitoring a load of anengine having a plurality of combustion cylinders; determining witherthe load meets criteria for cylinder deactivation; when the load meetsthe criteria for cylinder deactivation, selecting a number of combustioncylinders for deactivation and deactivating the selected number ofcombustion cylinders by deactivating an intake fuel injector, an intakevalve, and an exhaust valve of the selected number of combustioncylinders; monitoring at least one parameter indicative of the enginecondition; determining if the at least one parameter meets a thresholdfor adjusting the number of cylinders for deactivation; and continuingmonitoring the at least one parameter until the at least one parametermeets the threshold for adjusting the number of cylinders fordeactivation.
 137. The method of claim 136, wherein the at least oneparameter comprises one or more of an exhaust temperature, a brakethermal efficiency, a pollution level, and an exhaust flow rate of theexhaust stream.
 138. The method of claim 136, wherein the at least oneparameter comprises an exhaust temperature, and the method furthercomprises determining whether the exhaust temperature is within athreshold range or at a target temperature.
 139. The method of claim136, wherein the at least one parameter comprises a brake thermalefficiency, and the method further comprises determining whether thebrake thermal efficiency is above a brake thermal efficiency threshold.140. The method of claim 136, wherein the at least one parametercomprises a pollution level, and the method further comprisesdetermining whether the pollution level is within a threshold range orat a target level.
 141. The method of claim 136, further comprisingadjusting an air to fuel ratio to the active combustion cylinders. 142.The method of claim 136, further comprising adjusting one or more of thetiming or quantity of fuel injection, intake flow, exhaust gasrecirculation, valve opening or valve closing profile for the activecombustion cylinders.